SA Graan September 2018

September 2018

110

Special focus on mycotoxins

ycotoxins, toxic chemical com-

pounds produced by moulds,

can contaminate commodities

either in the field or during

storage and are invisible, odourless and

tasteless. The only proven way to deter-

mine whether grain, feed or food are con-

taminated, is by analytical testing.

According to the Food and Agriculture

Organization, food losses due to mycotoxin

contamination are estimated at 25% on

a global scale and pose a real threat to

food security, especially in Africa where

the magnitude of losses is difficult to esti-

mate because of a lack of information.

Mycotoxin production is foremost a food

safety issue, although the occurrence of

moulds can also lead to damage ranging

from rancidity, odour, flavour changes, loss

of nutrients and germ layer destruction

resulting in a reduction in quality. Most

mycotoxins are toxic in very low concen

trations, so this requires sensitive and reli-

able methods for their detection.

Effective management to prevent food

losses or adverse health effects as a result

of long-term exposure to contaminated

food is only possible when adequate reli-

able testing data is available. Well-timed

interventions in the food and feed value

chain can then be based on these testing

results.

The multi-mycotoxin assessments includ-

ed in the annual maize crop quality survey

for the past seven seasons provide the

most comprehensive overview of the multi-

mycotoxin risk in commercial maize pro-

duced in South Africa. Approximately 35%

of the maize crop samples were selected

every season for multi-mycotoxin analy-

ses to proportionally represent all the pro-

duction regions, as well as both white and

yellow maize.

The mycotoxins regulated in South Africa

are Aflatoxin B

and Aflatoxin total, Fu-

monisins (FUM) B

+ B

and Deoxynivalenol

(DON). These mycotoxins, as well as nine

other mycotoxins of most concern glob-

ally, are included in the LC-MS/MS analysis

used by the Southern African Grain Labora-

tory (SAGL).

In total 62% of the 2016/2017 season’s test-

ed maize samples contained one or more

mycotoxin, similar to the previous season

when 63% of the samples tested positive

for one or more mycotoxin. Co-occurrence

of mycotoxins is possible as either a re-

sult of contamination with more than one

fungus or the fact that several fungal

species are able to produce more than one

mycotoxin.

The absence of Aflatoxin B

, B

, G

Ochratoxin A, T2-toxin and HT-2 toxin in

the commercial maize samples over the

past six seasons were confirmed in the

2016/2017 season. The fact that Aflatoxin

, a mycotoxin classified as a cancer-

causing hazard, does not occur in com-

mercial maize produced in South Africa

(except for three white maize samples in

the 2014/2015 production season), is a huge

food and feed safety advantage for the

maize producers in South Africa.

Zearalenone (ZON) was detected in only

1% of the yellow maize samples and in

13% of the white maize samples, the high-

est value detected, namely 399 ug/kg was

in a white maize sample. Zearalenone in

white maize was found in five of the seven

provinces from which samples were recei

ved. Zearalenone in yellow maize was

found in North West Province and Mpuma-

langa. It must be noted that Zearalenone

was not found in any of the maize samples

from the Limpopo regions over the past

seven seasons.

The most predominant mycotoxins obser

ved in seven seasons in most regions

on both white and yellow maize are Fumoni-

sins B

, B

and Deoxynivalenol. With

the amendment of South African Regula-

tions in 2016 to include maximum allowable

levels for Fumonisins and Deoxynivale-

nol for human consumption, it is important

to focus on the percentage samples with

concentrations just below and above the

maximum allowable levels in unprocessed

maize, namely 4 000 µg/kg Fumonisins

+ B

and 2 000 µg/kg Deoxynivalenol.

The percentage samples with Deoxynivale-

nol at different concentration levels in the

2016/2017 season, is summarised for all

maize (white and yellow maize), white maize

only and yellow maize only, in

Graph 1

Graph 3

. Although Deoxynivalenol was not

detected in 63% of the maize samples, only

46,4% of white maize samples contained

no Deoxynivalenol.

It should also be noted that in 8,9% of

white maize samples and 2,3% of yellow

maize samples, Deoxynivalenol concentra-

tions above the regulated maximum allow-

able level of 2 000 µg/kg were measured,

with 7 698 µg/kg the highest concentration

observed on one white maize sample.

The number of samples that contained

Deoxynivalenol increased with 14% this

season, from 23% in 2015/2016 to 37%

in 2016/2017. The highest increase in per-

centage samples containing Deoxyniva-

lenol, was observed in the white maize

samples; from 26% in the previous season

to 54% of the samples this season. In five

of the provinces, the mean Deoxyniva-

lenol values of the white maize were higher

than the yellow maize mean values.

Less samples contained Fumonisins this

past season, with occurrences decreasing

from 57% previously to 44% of the samples.

Graph 4

Graph 6

are summaries of the

percentage samples with different Fumoni-

sin concentration levels in the 2016/2017

season for all maize, white maize and yel-

low maize. None of the white maize samples

contained Fumonisins above 4 000 µg/kg.

Values exceeding 4 000 µg/kg were meas-

ured in 1,2% of the yellow maize samples,

with one yellow maize sample reporting

6 059 µg/kg Fumonisins. The white maize

and yellow maize Fumonisins mean concen-

trations are similar in most provinces.

The different trends observed on the mean

concentrations of Fumonisins, Deoxyniva-

lenol and Zearalenone over the past seven

seasons in the different regions, confirmed

again the well-known fact that the myco

toxin risk in maize produced, differ from

season to season in the same region and

also from region to region. This can be

ascribed to the fact that the occurrence

and concentration levels of mycotoxins are

related to environmental factors as well

as seasonal climatic conditions during the

pre-harvest production period.

Crop overview

The all-time high record crop of the

2016/2017 season was more than double

that of the severely drought affected

2015/2016 season and 51,6% higher than

relevant

Jolanda Nortjé,

manager: Laboratory, Southern African Grain Laboratory NPC